Prunus crops within the Rosaceae globally form a homogeneous entity: they are geographically restricted to Mediterranean and temperate climates (Ramming and Cociu 1991) and comprise three major subgenera Prunophora (plums and apricots), Amygdalus (peaches and almonds) and Cerasus (sweet and sour cherries) (Rehder 1954). All wild species from which they have been domesticated are characterized by a low basic chromosome number of 8 (2n = 2x = 16) where Amygdalus and Cerasus are diploid while Prunophora range from diploid (apricots, Japanese and Myrobalan plums) to hexaploid (the domestic and European plums; 2n = 6x = 48) with intermediate ploidy levels existing within the wild plum species (e.g., P. spinosa; 2n = 4x = 32). Besides this low basic chromosome number, the size of the haploid Prunus genome of 280-320 Mb (Arumuganathen and Earle 1991; confi rmed by the peach genome sequence released in April 2010) makes it one of the smallest

among plants. This situation and coordinated research efforts favored the publication of a saturated map as earlier as 1998 (Joobeur et al.).